Enclosed case mud percussion tool



DeC- 22, 1964 R. BAsslNGER 3,162,251

ENCLOSED CASE MUD PERCUSSION Toox.

Dec. 22, 1964 R. BAssxNGER ENCLOSED CASE Mun PERCUSSION Tool.

2 Sheets-Sheet 2 Filed Jan. 19, 1960 u n z n 55/ LJ L? Aww@ NNNW 7,7-.g- L \v\ y n f f www? il A .w

/POJJ Bair/gef IN VEN TOR.

bis operable at high speeds with United States Patent Ofice 3,162,251Patented Dec. 22, 1964 3,162,251 ENCLGSED CASE MUD FERCUSSIDN "1300LRoss Bassinger, Rte., 11, Box 588, San Antonio, Tex. Fiied Jan. 19,196i?, Ser. No. 3,300 16 Claims. (Ci. 173-73) This invention relates tonew and useful improvements in percussion tools powered by anon-compressible hydraulic iluid.

Rotary bits, jars and other tools having reciprocating high speedpercussion elements operated by an incompressible hydraulic fluid havebeen widely in quarying stone, drilling oil and gas wells through hardformations and in other applications. The percussion mechanisrn of suchtools are of two general types; (l) those in which valves or percussionelements are spring actuated,and (2) those in which one surface of apiston driving a hammer in the tool is exposed to constant fluidpressure for driving it in one direction While another opposed largersurface is exposed to intermittent fluid pressure for driving it in theother direction with the admission of fluid pressure to the largersurface controlled by movement of the piston.

Each of these general types of tools has certain disadvantages. Forexample, springs become fatigued, break and have to be replacedfrequently when subjected to tension or compression at a speed of manyhundreds of times per minute. Differential piston type tools, astypified by U. S. Patent 1,096,886, eliminate the necessity for springsto operate valves or hammers but have a tendency to trap incompressiblehydraulic uid between the hammer and anvil forming essential parts ofsuch tools, thus cushioning the hammer blow and decreasing itseffectiveness.

It is an object of this invention to provide an improved percussion tooloperated by an incompressible hydraulic fluid in which cushioning of ahammer blow cannot occur.

Another object is to provide a percussion tool operated byincompressible hydraulic fluid in which spring actuation of hammer andvalves is eliminated.

j Another object is to provide a percussion tool in which build up ofsolids that may be present in the actuating hydraulic fluid on theopposed faces of hammer and anvil is substantially eliminated.

Another object is to provide a tool of this class that may be operatedat high speeds with little fatigue of valves and percussion elements.

Another object is to provide a tool of this class in which light weightlong wearing hydraulic fluid operated reciprocating valves of improveddesign give positive control of hydraulic iuid pressure applications.

Another object is to provide a tool of this class which substantially nowater hammer.

Still another object is to provide a tool of this class having areciprocating finger valve disposed to open and close an outlet forhydraulic iiuid from the tool in which the finger valve is hydraulicallyand positively prevented from entering and closing the outlet passageuntil after thehammer has struck the anvil.

Other objects, advantages and features of this invention will beapparent to one skilled in the art upon a consideration of the writtenspecication, the attached claims and annexed drawings.

In the drawings, wherein like reference characters are used throughoutto designate like parts:

FIGS. 1 and 2 are vertical sections through a preferred v embodiment ofthis invention. FIG. 1 illustrates an upper part of the tool and FIG. 2a lower part of the same tool, FIG. 2 being a continuation of and to beconsidered as joined to the lower end of FIG. 1;

FIGS. 3, 4 and 5 are vertical sections through a modication of this tooland illustrate sequential parts of a hammer stroke and show the valveand conduit relationships at sequential parts of the stroke.

The tool illustrated in FIGS. 1 and 2 comprises a housing designatedgenerally by the reference numeral 1. For convenience in manufacturing,this housing preferably is made of three parts; a short upper sub 2, anadjoining thick-walled section 3, and a lower thin-walled section 4.

The upper part of sub 2 preferably is vformed as a tool joint pin 5having threads 6 suitable for connection to a drill string. Sub 2 has aconduit 7 for entrance of hydraulic uid under pressure, which preferablyleads to a cavity 8 in the sub which in turn communicates throughseveral conduits 9 with a space 11 within the upper part of thethick-walled upper section 3. Sub 2 and section 3 preferably are joinedby tapered threads as illustrated at 12.

A cylinder 13 of proper size to iit snugly upon a smaller piston 14 of areciprocating finger valve designated generally as 15 is disposed in sub2 and communicates with the exterior of the tool through a purge duct16.

In cavity 11, in the upper end of thick-walled section 3, an annularspacer ring 17 having openings 18 therethrough is disposed and is heldin place by a spring 19. Annular spacing ring 18 and spring 19 eliminatethe necessity for close tolerance in the manufacture of the jointbetween sub 2 and the upper thick-walled section 3. Spacer ring 18serves as a limit for the reciprocating travel of finger valve 15 in adownward direction by supplying a surface which stops the valve bycontact with shoulder 21 on the valve. Variation or adjustment in theeffective length of the finger valve may be easily accomplished bychanging spacer ring18 for a ring of somewhat different thickness.Spring 19 functions merely to hold spacer ring 18 in lirm contact with ashoulder 22 formed on the upper thick-wal1ed section 3 and is notsubjected to flextion by movement of hammer 25. A linger portion 24 ofvalve 15 is slidably disposed through an opening in spacer ring 17.

A hammer designated generally as 25 is slidably disposed within housing1 for reciprocating movement. Hammer 25 comprises a smaller pistonportion disposed in the bore of thick-walled portion 3 and having auannular face 27 constantly exposed to pressure of actuating hydraulicfluid entering the tool through conduit 7, chamber 8, conduit 9, space11 and openings 18. Hammer 25 also has a larger piston portion 28, shownin FIG. 2, slidable in the larger bore of thin-walled section 4 of thehousing. Hammer 25 also has a portion of lesser diameter 29 below piston28.

Pistons 26 and 28 serve to keep the hammer axially aligned duringreciprocating motion in addition to furnishing surfaces against whichhydraulic fluid under pressure may act. Since hammer portion 29 belowpiston 2S is of smaller diameter than the bore of housing section 4; itleaves an unoccupied space 31 within the housing around this portion ofthe hammer and forms a continuation-of the space between the hammer andanvil.

A passageway for hydraulic fluid extends through the harnmer andcomprises an upper portion 32 and branch iconduits 33 extending from thelower end of upper portion 32 `to the space 31 surrounding part 29 ofthe hamfiner. The passageway through the hammer with an up- ;per centralportion 32 and several, preferably three, foranch conduits l33connecting with the space` 31 in the housiii-'gsuiioiii-iiiihg theiow'e' perror the haininon of some distance above .the -beati'g' f'ce"ofthe' hiiimh as iiihsir'aoo, eliminatessinfonia t t tigue andfailure'of the` ltvr of th met dueto this-canse;- Finger valve rsf niiportion 32 yi' triepas- `sage"ayonsso-dispeseoluint-fifi ifm-of diringe-ivoirenin ent-ei passagewaysain Arospo-nsoA fo positioning of thehammer iiear thel end' of` its up stroke and substantially closethepassageviiay to` fliidy o'yv. 'y Iiithe-1o" endof' "animer, 25g-aoaviiys4jis-fonned, 'oylin rioatporti'onslsgg Are= is posed-i within thiscavity andis retained therein by aii arnul'ar nut 3'7 which may bethreaded as Showri; Oi' held in" plac; hy-.si'np rings O1' otherconyiiientdev e.

Fihger 'valve'4 36 posedE siidhbly' cylinder 35@ ashoulder portieri 42;movement of the finger in cavity 34;` arid? allower iiiigei ii f ger'aininoiejnihsn-pision sa ons 'slidably disposed iii rtihihg' nut'- 37.Thev lower iir'tger 713 preferably is-hlibw withE its hollbwy interioririwardly tapering tbvvad 'shoulder 42 in order to 'reduce weight of theyall-ve andf to prevent metallic fatigue.: A purge passage 44extndslgitidially through thevalve; stem aridVI provides a4 passageway-foriliiid coiii`i`1i'nitatingv with the hollow interior of finger 43 andwith `cylinder 35@ he# hind' pis'bg. CylrideSS chmihicats with thehindieiiiteiiorfor-housinjgr In strook by hainiher-zs: spiiiiewayssoi siefoiihodi lateral sufra-oe 'or uiohoihhie'r- .Below piston 4s iii radio-1alignment with s'fpiinowys 51Al in: uioio'we-rehdorb-ousingy Beaiings'52l oie-uisposedwithih meis-'eline nys ond permit relative longitudinenier/ement between the nii-vii ano-housing whiiopfievontingfreisnieifotoiion Ythoreb'etweeh;

fnl 'ii-opeipis'fon portion sisi' irs-- The low-sr ond of the hon-sings3: is equipped with-snifi 'able means for attaching-cto. a fooi sfshere shown as threads 54a AI "passV "ay foroperating hydrauli Huidextends .from 'the fof itiieiivii-45t-through@ vil and tool to 'apoint-'adjacent rof'avr'orlc'sri ne' :P wayfss i'sfaxally'lighedi withifinger- `4 .of 'valve-3 that nger 43, may move forward to enter and'substanf tially closepassageway v`56 when pressure in 'pa's's'ageway56issuflicientlyrducedt Y v 'I/ A means for hydraulicallypreventingfentranoe of n'ger 43v into'pass'ageway-SE until: afterhammer: i251 has jstrucli the anvil in its 'reciproca-thigvtrave'lisprovided.lk'1`hisV means comprises grooves 57A 'out into the' foefof theham#-l hier.v These grooves-preferablyare threeinfiiurhbera dl are`radiallyY disposed to communicate with passageway- 56 kand with 'spaceS17-in the housing around. the 4hamihei and below piston 2 8'. T-Theg'ro'ovesxare located at 'the sui-innig interino@ 'of' the iinininef1an-d 'anvil anni should have a total crosssectional Aarea amountingboltl) nero-oni Vof'uiot*ofionssngs y sog-*nissen jihin oop-@nainsiin-on hie fyn o io used desired; grooves 57 .could be located` in theanvil fac'c, orv be formed ogs-aligned groove-sin -b-o-th hainiiier andanvil; 'i

considering FIGS. 3, 4'and 5 which illustrate a tool substantiallyidentical with that just described in FIGS. l and 2, except that spring19 in cavity 11 is omitted.

FIG. 3 illustrates the position of the parts of the toOl at the instantafter impact of the hammer with -the anvil. Incompressible hydraulicfluid, preferably drilling mud, may be considered as entering throughsupply conduit 7, cavity 8, conduits 9, cavity 11 and openings 18 intothe interior of housing 1. The full operating pressure is thus yappliedagainst lthe lower surface of upper iinger valve 15, driving the valveupward tothe full limit of its reciprocating travel andjholdingit inraised position'. There is also some flow of operatihg fluid throughthelongitudinal purge passage in the stemof valve v15 into cylinder 13and to .the exterior of the tool through vent 16. Flow of huid throughthe purge vpassage in the valve stem,VV cylinder 13V and verit I6substantially eliminates water hammer, maintains 'pressure' inoyl'ii'rder 13' between the pressureai whichoperatingiluid is supplied.and that' at'the' outside 'or the tool; 'purgeisi cylinder"- -13 orany; accumulationof 'f soiii4 partidosand insures suhstaniiouy constantflow fr mj cylinder 1'3 to thejoutsideofthe' tool, thus yprevenu Sandi'rock chips and other abrasivemattei' from being drawn intovcylinder",'13. l 'ressur'e of' acttiii'g-iluidirr the body cavity is V appliedageway' 32' in 'gvthe' hammer' and, branch pas= sageways 3 ofthespu-ce31 aru'nd the l'owerptlrt of the hammer 'within casing l and" from this"space through pen'iiigs' 378` intoL cavity 34 in the lower`V part' ofkthe y "fis In positiojirof parts' show-n; pressure from' the huidilowing through passageway 5'6 inthe anvil has justy been reducedbycontact of 'oppbsingfacesof the hammer and anvil". ofactuatingiliiidthrough`A grooves Sfhas effectively preventedirapping`i'rieonipi-e'ssihlehydraulic iuidV bct'w'cen thenhainmer and ahnL-facesbut uponcorrtact of the faces' the restrictioh 'of bw areatothat of thetotal cross section `of these grooves'has result-:cd ih' a pres= suredropin conduit 5'6. Y A

FullE pressure of op'er'ath'g' fluid however is upon'v cavity 34up---the upper sideV Of' 'the shoulders of the Hilger yalyedispose'd'thcrcih. part of this' prs'sliiiete'ndiiig to drive theViin'ger valve dow-n intoE closingposiiioii in passageway 56 is balancedby pressurev in the oppositediretti-o" `'u poi'i the lower s'i'deofpiston 39", Bot-Whe lower 'iid-f the yal-"vev irige'r 'hasanf' area muchl'arg'er than that ofpiston'39-L "The reduction iii pressure up'onthelower end of the 'valve finger caused by Contact of the hammer adivilfaces with 'resultiiigf restriction ih rhou/way* cross section hasa's'ed' the lingervalve`- tobe d'riv'eit-- into and substantiallyclose-'passageway 551.` I

'through pass f '3i in the housing andV grooves-57 to the fase 'ofv the,upper iingervlve; 'the lower end off the lower' ringer vaiveisdrownout-or passageway 'sjhy h afnrh-er travel;

i Asf soonY aslthe lower-endi of-theupper' ng'er valve ating pressureapplied to; the annular surface 2'7 ofVv L the smaller upper piston-,ofithe hammerthus arresting its @Warst-matige and; Staffing.- thelenimer 9aits .Power stroke. As thev hammertrayel's, downward: i'n-it s powerl"shore if' is' neoesssiy that the iiiooiii'pisssibiehydiouiio fiuid bemoved outward through passageway 56 from the space between the decendinghammer face and opposing anvil face.

Since this fluid has some viscosity and inertia there will be backpressure upon the lower end of the lower finger valve which issufficient to keep the valve in raised position. At the same time, thereis a flow of some of this iiuid through the longitudinal purge passagein the valve stem and outward through Vvent 45 into a space in thehousing above piston Z8. Since this space is variable in size accordingto the position of the hammer, flow of liquid upward through the purgechannel and vent into this space and outward through openings 60 and 61in the body substantially eliminate entrance of sand, stone chips andother abrasives through openings 60 and 61 in the housing 1. The partisremain in the relative position shown in FIG. 4 until the instant beforethe hammer strikes the hammer face.

At this instant hammer travel disengages passageway 32 from the lowerend of the upper finger valve 15 and pressure again builds up inpassageway 32, branch passageways 33, space 31, passage 38, space 34,grooves 57 and in the narrow space between the anvil and hammer. Thishydraulic pressure effectively and positively maintains the lower fingervalve in its raised position and prevents its engagement with passagewaySe in the anvil until after the hammer has struck the anvil. At theinstant the hammer strikes the anvil, ow of fluid into passageway 56 andpressure below the lower end of the lower finger valve is restrictedbecause of the smaller area of grooves 57 as compared to thecross-sectional area of passageway 56. Grooves 57 also function at thistime to draw off fiuid between contacting faces of the hammer and anvilwithout any cushioning effect due to retained fluid between thesesurfaces.

Reduction of pressure below the finger valve is not accompanied byreduction of pressure in cavity 34 and therefore the unbalanced part ofthe force applied by the fluid to the shoulder of the lower finger valvedrives it downward into passageway 56 at very high speed, cutting ofi?flow of fluid therethrough, and the cycle of operations is repeated.

It will be seen that in addition to effectively preventing anycushioning of hammer blows upon the anvil face, the provision ofwithdrawing fiuid from between the facets made by continuation of flowthrough grooves 57 permits the faces to be scoured by fluid extrudedfrom between them. This scouring action of the drilling mud isespecially important when it may contain grit or other materials whichmight build up into hard deposits under the force of hammer impacts. Ifallowed to accumulate such deposits frequently lcause .spalling or otherdeterioration of the striking surfaces. Build up of deposits andspalling are effectively prevented in the tool of this type.

The purge passageways in the valve stems of both valves permits flow offluid through their respective cylinders and so prevent accumulation ofdeposits in these cylinders and entrance of abrasive particles. Thispurge passageway also is effective in reducing water hammer.

`The particular design of finger valve used has been found to be veryeffective in reducing metallic fatigue so that the valves are longwearing under severe operating conditions.

The velocity of valve travel in reciprocation can be predetermined bychoosing a size of cross-sectional area for vent passageways 45 whichgives the required speed of valve operation while reducing the impactload.

n From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the apparatus.

It will be understood thatcertain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the lscope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that allmattter herein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. A hydraulic percussion tool comprising in combination a housing; ananvil slidably disposed in an end of the housing; a hammer slidablydisposed within the housing for reciprocating movement to beat upon theanvil, said hammer having a first piston surface constantly exposed tohydraulic pressure tending to drive it in one direction and a secondlarger piston surface intermittently exposed to hydraulic pressure todrive it in the opposite direction; a supply conduit for hydraulic fiuidunder pressure disposed to introduce said fluid into a space in thehousing behand the first piston; a passageway for hydraulic iiuidthrough the hammer, communieating with said space behind the firstpiston and with a second space within the housing beyond the secondpiston and between the hammer and anvil; a reciprocating hydraulicallyactuated finger valve, responsive to position of the hammer, disposed toenter and substantially close said passageway near the end of the backstroke of the hammer and disposed for sufficient length of reciprocaltravel to remain in said passageway during a substantial part of thepower stroke of the hammer; a second passageway for hydraulic fiuidthrough the anvil, communicating with the space in the housing betweenthe hammer and anvil and with the exterior of the tool; a secondrhydraulically actuated reciprocating finger valve carried by the hammerin positionto move into and substantially close the passageway throughthe anvil after contact of the hammer and anvil; and hydraulicllyactuated means for preventing movement of said second finger valve intothe passageway through the anvil until contact of hammer and anviloccurs.

2. The tool of claim 1 wherein the hydraulically actuated means forpreventing movement of the second finger valve into the secondpassageway comprises a third owway, having lesser cross-sectional areathan the passageway through the anvil, leading from the space behind thesecond piston tothe passageway through the anvil, disposed where it isnot closed by contact of hammer and anvil but is closed by the fingervalve on movement of the valve into the second passageway.

3. The tool of claim 2 wherein the flowway is a plurality of radialgrooves located at the interface of hammer and anvil.

4. The tool of claim 3 wherein the liowway is a plurality of radialgrooves in the hammer face. y5. The tool of claim 4 wherein the radialgrooves have a total cross-sectional area amounting to about percent ofcross-sectional area of the passageway through the anvil.

6. The tool of claim 1 wherein each of the reciprocating linger valvesis disposed in a valve retaining member and comprises a smaller pistondisposed in a cylinder cornmunicating with the exterior of the toolthrough a vent passageway entering the cylinder at a point furtherwithin the cylinder than ythat reached by the piston at its maximumdistance of travel and a finger slidable -in said valve retainingmember, said finger having a larger piston surface than thesurfaceof thesmaller piston opposed to the smaller piston surface; a shoulder'on saidlinger part disposed in a cavity between said valve retaining member andsaid cylinder and having an annular efectivearea equal to the differencebetween the area of the piston surface of the finger and-the area of thesmaller piston exposed to pressure of fluid withinv the cavity; a stemconnecting said smaller pistonand said finger, said stem having a purgepassageway therethrough extending through said finger, through saidsmaller pist'on, and communicatingawith said cylinder behind 'thesmaller piston; andA means for varying pressure on' the largerpistonsurface; on the finger part', Varid on said annulararea o'n saidrshoulder responsive to 'movement ofthe hammer to cause reciprocationlofthe finger.

7l The tool of claim 1- whereintlle secondl reciprocating finger isdisposed in a| valve retaining member carried by they hammer, andtheva'l've comprises asmaller piston disposed for. reciprocation in acylinder in the'hammercommunicating with the exterior of the toolthrough a vent passageway/connecting the cylinder at a pointr furtherwithin the cylinder .than that reached bythe smaller piston at its oftravel, with, a space within the body around the hammer betweenVthetpiston surfaces of the hammer, and through openings in the bodycommunicating said space; afinger slidable inV the valve retainingmember andhaving a, larger piston vsurface opposed to the smallerpiston; a,4 shoulder on the finger disposed in a cavity in the hammerbetween the valve retaining member and the cylinder and having an.annular area equal to theditference in area between the area of theYpiston surface of the finger andl the yarea of the smaller pistonyexposedto pressure of fluid within the cavity; a stem connecting: theV'smaller piston and the finger; a purge passageway extendinglongitudinally through thestem, fingerv and smaller piston communicat-Vingl with the interior ofthe cylinder behind `the piston; and means,comprising openings from the cavity intoja space in Vthe, bodyVsurroundingthe strikingendlof the hammer, for varying pressure on thelarger piston surf` face and on said annularl'areaof the shoulder,responsive to movement of the hammer,l to cause reciprocation Vof theyfinger. Y

8. The tool of claimfl wherein each of the reciprocating finger valvesisdisposed iny a valve retaining member and comprises a smaller pistondisposed in a cylinder communicating with the exterior of the toolthrough a vent passageway entering the cylinder at apoint further withinthe cylinder than that reached' by the piston at its maximum distance oftravel; va finger slidable, in` said valve retaining member, said fingerhaving a larger pis*- ton surfa'cethan the surface of the` smallerpiston, opposed to the smaller piston surface;Z a* shoulder ony saidammassi thecavity; a stem connecting thesmaller piston' in the finger; apurge' passagewayV extending longitudinally through the stem, finger andsmaller piston communicating with the interior of the cylinder behindthe piston; and means, comprising openings 'from' the cavity into aspace in the body surrounding-,the lstriking end ofthe hammer, forvarying pressure on the larger piston surface andv on-said annular arealof the" 'shoulderresponsive v to movement of the hammer to causereciprocation of finger party disposednin a cavity'between said valveretain.- Y f ing member and said; cylinder and having anv annulareffective'.v area equal to-l the difference between the area ofthepiston surface of the finger andthe' Yarea of the smaller piston`exposed to pressure of fluidvwithin .the cavity; a stem connecting saidsmaller.,pistony and said finger, said stem having a purge passagewaytherethrough extending .through the finger, rthrough said smallerpiston, and comunicating. with 'said cylinder behind' the piston; andmeans'for varying pressure yon the largerpiston surface on the finger'part,A and on said annular -a'realon saidv shoulder responsive ',tomovement of theV Vhammer to'cause reciprocation of the finger.l l ,Y

9. The tool" of claim 1f wherein'theisecondreciprocatingl fingerisdisp'osed in a valve reta ingme'nfrb'er carried by the' hammer, andthe Vvalvecomprises 'aj-smaller pis- V'tondisposed for reciprocatiniin acylinder in the hammer Acornnrunieatingwithfthe exterior of the/toolthrough the bodyfia'round l'the hainrrier'betweenr the piston sur- L avent'V passageway ,conne'clitingJ thejcylinder, at a point Ylfurther'vvithin the cylinder than that reached' by Vthe fat-:esI ofthehammer, andfthrough openingsA in the bod'y d communicating-'with saidspace';` afnger slidahley in the i 'valve retaining inember Yand'havirlg al l'a'r-ger piston Asur-- face opposed ltothesr-rlalleriinistoinfav shoulder on the fiilge'r/,- disposed in aca in;the llarunner. between the valve retainingmembe'r an'the.cylinderand'having. 311,1V

the fingen l v 1'0. In ahydraulicpercussion tool wherein a hammer isslidablyl disposed in' a-liousingl to beat upon any anvil, said hammerhaving a piston surface tending to move the hammer away from the anvil:upon whichphydraulic pressure is alternately increased' and` diminishedto cau's'e reciprocat'ion of the hammer, and means for intermittentlyadmitting hydraulic` fluid to press uponv said piston surface isprovided, the improvement which comprises an outlet passageway forhydraulic fiuidth'rough the' anvil; a' hydraulically actuatedreciprocating finger Vvalve mountedl inthe hammer and disposed; to moveinto and close the passageway through the anvil`upon Contact o f thehammer with the anvil; and` hydraulic means forV `preventing movement'of" s aid finger valve into' said' passageway through th'eanvil Yuntilcontact of hammerand anvil occurs'. Y

1,11. The' tool' of claim l0 wherein'the hydraulc'means V,for preventingmovement of" the finger valve' into the passageway comprises a fluidflowway, having lessercross'- sectional arear than the passagewaythrough the anvil,I com'- cunicatingwith the passageway through theanviland with a Vspace within the housing between the anvil and said pistonso disposed that it is not closed by contact of hammer and anvil but is`closed by the finger valvev on movement ofthe valve into the passagewaythrough. the anvil. Y

` 12. TheV t'o'ol of claim l1 wherein the liowway is a plurality ofradial grooves located at the interface of hammer'and" anvil. y A y 13.The toolof claim llpwherein the flow'way is a plurality of radialgrooves inthe hammer face'.

k14. The tool. of claim 1l wherein the rad'al'g'rooves have' a totalcross-'sectional area amounting to about v90 the, surface of the smallerpiston opposed to the smaller piston surface; ashoulder'on said fingerpart disposed in a cavity within thezhammer between said valve retainingmember and said cylinder, Ysaid shoulder having an annular effectivepiston area equal to the difference between the area of the piston'surface kof the finger and the area ofthe small'erpiston, exposed topressure of fluid in the cavity; astemconnectingvsaid smaller piston andsaid fingen'saidstem having ajpurg'e passageway therethrough-extendingthrough said finger, through said smaller `piston Vandtoinmunicatingwith said cylinder behind they piston; and means for varying pressure onthe larger piston surface of they finger part, and on said annular, areaon said shoulder, responsive tomovement of the hammen; tocausereciprocation of the finger.

annular 'area equal toV "the d1fl`erence`in 'area betweelrifA the'areauo'f Y A s bt smaller piston 'exposed to pressure or fluid within16. In a hydraulic percussionrtool wherein a hammer is slidably disposedina housing .to beat uponvan anvil,

saidfhafmmer having a piston surface tending to move. fthe lhammer awayfrom:V the anvil upon'whichhydraulic pressure -is Yalternately increasedand diminished to cause reciprocation'of the hammer, and means vforyintermittent- 1y admitting hydraulic iiuid to press upon said pistonsurface is provided, the improvement which comprises structure includinga portion of said housing extending around and enclosing said hammer anda portion of said anvil and supporting said anvil in slidingrelationship Within the lower end of said housing, annular passagewaymeans within said housing around the lower portion of said hammer andthe upper portion of said anvil, a cavity formed in the lower portion ofsaid hammer, passage means through said hammer connecting said cavityand said annular passageway, an outlet passageway for hydraulic fluidthrough the anvil, a hydraulically actuated reciprocating finger valvemounted in said cavity extending through the lower end of the hammer anddisposed to l@ move into and close the passageway through the anvil uponcontact of the hammer with the anvil, and hydraulic means for preventingmovement of said linger valve into said passageway through the anviluntil contact of hammer and anvil occurs.

References Cited in the file of this patent UNITED STATES PATENTS1,096,886 Bayles May 19, 1914 2,620,162 Pennington Dec. 2, 19522,756,723 Bassinger July 31, 1956 2,774,334 Cline Dec. 18, 19562,786,451 Dulaney Mar. 26, 1957 2,859,733 Bassinger et al Nov. ll, 1958

10. IN A HYDRAULIC PERCUSSION TOOL WHEREIN A HAMMER IS SLIDABLY DISPOSEDIN A HOUSING TO BEAT UPON AN ANVIL, SAID HAMMER HAVING A PISTON SURFACETENDING TO MOVE THE HAMMER AWAY FROM THE ANVIL UPON WHICH HYDRAULICPRESSURE IS ALTERNATELY INCREASED AND DIMINISHED TO CAUSE RECIPROCATIONOF THE HAMMER, AND MEANS FOR INTERMITTENTLY ADMITTING HYDRAULIC FLUID TOPRESS UPON SAID PISTON SURFACE IS PROVIDED, THE IMPROVEMENT WHICHCOMPRISES AN OUTLET PASSAGEWAY FOR HYDRAULIC FLUID THROUGH THE ANVIL; AHYDRAULICALLY ACTUATED RECIPROCATING FINGER VALVE MOUNTED IN THE HAMMERAND DISPOSED TO MOVE INTO AND CLOSE THE PASSAGEWAY THROUGH THE ANVILUPON CONTACT OF THE HAMMER WITH THE ANVIL; AND HYDRAULIC MEANS FORPREVENTING MOVEMENT OF SAID FINGER VALVE INTO SAID PASSAGEWAY THROUGHTHE ANVIL UNTIL CONTACT OF HAMMER AND ANVIL OCCURS.